Alternate Power Supply - Meanwell RSP-320-24  

Active Member

This is my alternative power supply for the MK3 printer.
As shown in the hardware thread, the stock one seems slightly underpowered. I decided to replace the stock power supply with a meanwell 320W power supply (RSP-320-24). The LRS-350-24 should also fit this housing, but I haven't tested - please feel free to test and comment. The fan on the meanwell will be the loudest aspect of the printer now - but personally, I don't find the meanwell fan to be that loud anyway.

This is printed in transparent yellow PETG from Prusa. It took around 10 hours to print with .2 layer height and 50% infill. You can likely go less than that if you want.

Here's how to make the swap.
CAUTION: This requires dealing with AC and DC power wires. Care must be taken.

Parts Required:
1x Main Housing (Thingiverse files)
1x Bottom Cover (Thingiverse files)
1x Side Bracket (Thingiverse files)
5x M4 - 8mm countersink screws (purchase)
4x square nuts for 3M screws (pulled from stock power supply housing)
4x M3 countersink screws (pulled from stock power supply housing)
2x M4 nuts
2x M4 screws (used on frame/stock power supply)
14AWG power wire and spade terminals (heat shrink tubing if using bare spade terminals)
1x washer (for setting the M4 nuts)
1x M4 screw for setting the M4 nuts - you should be able to use one of the 2x M4 screws from the frame.


1. Print the 3 parts

2. Dry fit the parts to ensure they fit. Sand/finish any surfaces that require it. The bracket has a tab that slides into the main housing. The outside edge of the main housing should be flush with bracket when join. Use your favorite glue to secure the two together. Be careful not to get glue in the screw/bolt holes. Use a couple of clamps to securely hold it together while drying.

3. Once the glue has dried, use a washer and M4 screw to set the M4 nuts into the side bracket and main housing. Take care and do not over tighten. Just enough to set the nut in place and that it is flush with surface.

4. Remove the stock power supply from the Prusa i3 MK3 printer. Remove the bottom cover. Pay attention to the wiring and note their positions. Good idea to take a photo of the wiring for reference later. Use a piece of masking tap or other tape to mark any wires you want to take note of. Carefully, start unplugging the AC wires. These are the wires attached to the IEC outlet and the switch. Note the positions of Live, Neutral and Ground.

5. Carefully remove the stock power supply from its housing. Pay attention to the small red wire as this is attached to the power panic circuit board. Do not break this wire. Unscrew the terminal this wire is attached to at the PSU side and gently remove. Once removed, remove the Live, Neutral and Ground wires from the PSU. We will not be using the VDC wires attached to the PSU, so you can set the PSU and VDC wires to the side now.

6. Remove the IEC outlet and power switch from the old housing. Place into the new housing in the same position as the old housing.

7. Connect your new VDC wiring to the meanwell PSU. Pay attention to VDC+ and VDC- lines! Be sure that you have properly crimped the wires and added heatshrink if needed (only needed if you use bare space terminals. Connect the Live, Neutral and Ground wires paying careful attention to the correct terminals on the meanwell supply. NOTE: The photo below is a reference photo only. Do not yet attach the Power Panic sense wire or the IEC.

8. Carefully slide the wires in from the top of the new housing. Do not yet push the power supply into the housing. Start by connecting the sense wire to the VDC+ terminal. Once connected, you gently slide the meanwell supply into the housing.

9. With the power supply fit in, you can connect the power switch and AC lines to the IEC outlet. Pay very close attention to the wiring! Did you take that photo mentioned in step 4? Now is a good time to reference the photo.

10. If needed, adjust the power supply to align with the screw holes. Use 5x M4 - 8mm countersunk screws to secure the housing to the PSU.

11. Place a square nut into the slot on the housing side. Place 3x square nuts into the slots on the bottom cover side.

12. Arrange the cable so that it has a bit of slack within the housing. You can use a cable tie if you like to help with this. If you use a cable sheath like I have, it will be a tight fit. Take care as you don't want to place any unnecessary strains on the cabling. Secure the bottom cover to main housing and you will end up with a nice new power supply ready for installation.

Installation of the power supply follows the same procedure as from the manual. If you have used a cable sheath like I have, be sure that it does not interfer with the Y-axis. Cable ties are your friend here 🙂

Be sure to run a calibration again - but you know that 🙂
Happy Printing!

Posted : 16/04/2018 3:48 am
Estimable Member

Nice job!

Posted : 16/04/2018 4:35 am
Estimable Member

Nice design to make it work with the stock wiring length. I used a different design off Thingiverse and had to lengthen my power cables.

Posted : 16/04/2018 5:33 am
Active Member

I didn't use the stock power wires. I replaced those with new 14 AWG wiring. They are slightly longer than the stock ones, but not by much. The nice thing about replacing the cables is that you can get them cut to the right lengths. I found some of the stock cables to be longer than necessary.

Posted : 16/04/2018 5:37 am
Eminent Member

hi, i think ill do this as the first thing i do/print when i build my printer. i dont like the thought of potential fire hazards. just curious if PETG is a must for these prints? i think its the more heat-stable plastic over PLA? iv ordered a few rolls of PLA so i have stuff to print with once the kit arrives, but no PETG.

I also decided to go with the LRS-350, since the size is the same, and i guess the extra 30w cant be a bad thing. I assume there are no considerations or modifications i need to make to your instructions to use that model instead?

thanks for the write up!

Posted : 29/06/2018 9:44 pm
Reputable Member

I notice from your photos that the Meanwell as an extra set of 24V connections. I assume from the layout of those connections that it is a single rail internally. If so it would make sense to move the power panic to the spare +24V connector to ensure a good connection rather than have it squeezed in with the Ensiy electronics +24V one.



Martin Wolfe...
Posted : 30/06/2018 3:03 am
Estimable Member

How often does the PS fan turn on during PLA printing?

Is the fan noise much louder than no PS fan?


MK3 Kit, Designed, built 4x4 CNC Plasma Cutting Table, Motorcycles Bigdogbro's Adventures
Posted : 03/07/2018 5:36 pm
Active Member

The RSP-320-24 fan is constantly on.
It is by far the loudest part of my printer. The 1" case size also makes it difficult to find a quieter fan to put into it as the selection of quiet, thin fans with the same RPMs are tough to find.

I actually spoke to meanwell about this, and they mentioned that if I wanted something quiet, I should go for the UHP-350-24 or the UHP-500-24.
However, because those units are fanless, they say you need to mount them onto a metal plate to ensure the heat can dissapte.

I haven't looked into either of these yet, but these might be a really good option if doing the lacke or other enclosure where you want to put the PS away from the printer.

Posted : 13/07/2018 5:32 am
New Member

What kind of glue did you use for this?

Posted : 16/10/2018 4:41 pm
Active Member


I am using a Meanwell RSP-320-12 on my MK 2.5s  and have come across a good method of reducing the fan noise...

First step is simple:  a great amount of noise is not from the 6ox10mm fan itself, but from the very restrictive opening stamped into the case. So, I just cut out the opening to make a round hole and installed a regular wire fan guard / grille.  This both reduces the noise and makes it a much less annoying sound. It probably improves cooling as well.

Second step involves finding a quieter fan, but there is not much available in 60x10mm .  Quieter fans are made in 60x15mm and 60x25mm, but those are too thick to fit inside the RSP-320 series. It is possible to mount the fan on the outside the housing, if you don't mind the appearance and bulk.

Third step is modifying the fan control circuitry of the RSP-320, to provide a lower voltage to the fan.  This is risky, as the fan might fail to start spinning at a lower voltage and overheating is possible with less or no airflow. As the RSP has no fan speed monitoring, this is probably not a good idea.

I tried mounting the fan to blow heated air out of the RSP-320 instead of blowing cold air in, but this resulted in dramatically hotter running. 

¡no entiendo Español!
Nein! Nicht Versteh!
Я немного говорю по-русски но не очень хорошо, и...
I'm not very good at English either! Maybe someday I'll find a language I'm good at?...
Posted : 12/07/2020 7:17 pm
Karl Herbert
Famed Member


I use a Meanwell RSP-500-24 for my MK3/MMU2S. The built-in fan was too loud for me and so I replaced it with a silent Noktua fan.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 12/07/2020 8:50 pm
New Member

Thank you!   Worked perfectly.  I used the LRS-350-24.  Zero fit problems.  Opted to use supports on the main body just to be safe.   I didn't want to tear up the original base to get the four square nuts out so I drilled a tiny hole above each and pushed them out with the drill bit.


This post was modified 1 month ago 2 times by carl.p4
Posted : 14/07/2020 8:52 pm

Please Login or Register